1. Field of the Invention
This invention relates to an orthodontic molar buccal tube having a cover which may be opened to convert the tube to a bracket.
2. Description of the Related Art
In orthodontic treatment, an arch wire is placed in slots of tiny brackets that are fixed to anterior, cuspid and bicuspid teeth. The arch wire forms a track to guide movement of the teeth toward desired positions for orthodontically correct occlusion. Typically, ends of the arch wire are held by buccal tubes that are secured to molar teeth.
Convertible buccal tubes are used by orthodontists during an early stage of treatment. The tube is somewhat similar to an orthodontic bracket having a slot, but has a plate or cover to close the slot and form a tubular opening that is typically rectangular in cross-section. The plate can be removed when desired to open the slot and thereby convert the buccal tube to a bracket.
Convertible buccal tubes are often used on the first molars of younger children who do not yet have second molars. In earlier stages of treatment, the buccal tubes on the first molars serve as anchors for the terminal ends of the arch wire. When the second molars erupt, brackets or buccal tubes are mounted on the second molars to function as new anchors for the terminal ends of a longer arch wire. The cover over the arch wire slot of the buccal tubes on the first molars is removed before installation of the longer arch wire to convert the tubes to brackets and enable the orthodontist to carry out edgewise treatment mechanics on the first molars.
Buccal tubes having removable covers extending over arch wire slots are described in U.S. Pat. Nos. 3,391,461, 4,820,151 and 4,927,362, all of which are assigned to the assignee of the present invention. Other convertible buccal tubes are described in U.S. Pat. Nos. 3,838,514 and 4,498,867. The slot covers described in these patents are removable as a single piece from remaining portions of the buccal tube using a pliers-type tool, a prying device or some other type of tool when it is desired to convert the buccal tube to a bracket. The cover shown in U.S. Pat. No. 4,927,362 is integral with remaining portions of the bracket and is removed by shearing the cover along lines of weakness next to sidewalls of the arch wire slot.
It is possible, however, for the cover to be dropped into the oral cavity during conversion of such buccal tubes to brackets. For example, an orthodontist using a pliers-type tool may unintentionally loosen the grip on the tool handles during or after the conversion, causing the cover to drop from the jaws of the tool. When using a prying device, the cover may drop into the oral cavity if the cover is separated from the buccal tube before being grasped or otherwise retained. A cover that has been dropped in the oral cavity often can be retrieved, but such occurrences represent an inconvenience both to the orthodontist as well as to the patient.